Classical analysis of polymeric compounds such as rubber compounds for identification of additives such as accelerators, antioxidants, and antiozonants require a very difficult separation step of such additives from the rubber compound prior to analysis. Thermosetting polymers such as vulcanized rubber are even more difficult to analyze than thermoplastic polymers due to the compounding ingredients being locked into the matrix by carbon black and crosslinking of the rubber polymer. The classical method for separating volatile additives from rubber is by solvent extraction. Modern separation techniques such as thermogravimetric analysis (TGA) or pyrolysis will produce volatile fragments of additives, but these modern separation techniques are quite complex and result in incomplete analysis due to poor resolution and the inability to separate oligomers of polymer and oil. A further problem inherent in most thermosetting rubber mixtures evolves from many of the additives being already fragmented due to the curing and crosslinking process. Existing extraction techniques produce fragments while the modern thermal methods produce highly fragmented products as well as create interferences from the polymers and organic softeners. Desorption methods such as TGA cause further fragmentation of the fragmented additives thereby preventing recovery of the original fragments.
A current prior art method of analyzing additives to vulcanized rubber compounds involves direct insertion of the vulcanized rubber into an ion source of a mass spectrometer, but this does not allow for the selective separation of process oils or volatile fragments, and further produces a complex spectrum containing ion fragmentation of the entire compound. Limitations on the small sample size render it difficult to detect the typical low concentrations of volatile additives in conventional rubber compounds. A further problem of the direct insertion method relates to inefficient extraction and isolation of the organic additives from the inorganic additives primarily due to carbon black matrices. The direct insertion method typically requires frequent and costly maintenance of equipment due to the deposition of large amounts of non-volatile material on the ion source.